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Juluri Rao*, John Moore, and Andrew Stewart

The EU Regional Draft Waste Management Plan (1999-2004) identified pig slurry (501,590 tonnes), poultry manure (217,110 tonnes) and spent mushroom compost (221,665 tonnes) as the main contributors to the 3.5 million tonnes of waste generated annually in Ireland. Current legislative restrictions prevent pig wastes from intensive pig units and horticultural wastes mainly spent compost produced in mushroom farms being disposed via landspreading due to pollution threat from nutrient run-off and the health hazards due to animal and human risk pathogen contents in wastes. Composting is a world-wide popular option for environmentally sustainable means of recycling farm wastes. In Ireland, profitable conversion of farm wastes such as pig slurry solids and spent mushroom compost has not yet been fully explored for their economic viability as `green' fertilizers. In this study, we produced pelleted formulations of the composted pig waste solids, (20%) blended with spent mushroom compost (26%), turkey litter (26%) cocoa husks (18%) and shredded paper (10%) to an environmentally safe, organic-based fertiliser resulting in N:P:K = 3:5:10, ideally suitable for use on amenity grassland such as golf course fairways and greens in Ireland, wherein spring and summer fertilizers with slow release of nutrients would aid an even growth of grass. We describe the composting methods used, processing technology developed and additional amendments such as dried blood or feather meal that were used during the pelletisation operation yielding specific N:P:K target ratios from the pig manure and spent compost wastes. We also report on the rigorous microbiological tests carried out throughout the composting phase and ascertained the pathogen-free status of the final pelletised fertilser products.

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Steven J. Bergsten, Andrew K. Koeser, and J. Ryan Stewart

Long used as a source of food, beverages, and fiber, Agave exhibits potential to be cultivated as a crop to produce alternative sweeteners, bioenergy, and a variety of other end uses. However, little is known regarding the productivity levels of Agave when grown in saline soils in semiarid regions. Hydroponic experiments were carried out to evaluate the effects of salinity on biomass accumulation and nutrient levels of young plants of Agave parryi, Agave utahensis ssp. kaibabensis, Agave utahensis ssp. utahensis, and Agave weberi. Salinity treatments (0.6, 3.0, 6.0, and 9.0 dS·m−1) were imposed in each experiment. Both subspecies of A. utahensis were sensitive to salt treatments. In the higher salinity treatments, A. utahensis ssp. utahensis exhibited high mortality; both subspecies had lower plant dry weights. Agave parryi was more tolerant, but experienced a decrease in plant dry weight in the 9.0 dS·m−1 treatment. The biomass of A. weberi was unaffected by any level of salinity. Calcium, Mg, S, and Mn levels decreased in both A. parryi and A. weberi at higher salinity levels. Potassium and P levels in A. parryi decreased in the higher salt treatments. Decreases in nutrients were not severe enough to cause any apparent nutrient deficiencies in A. parryi and A. weberi. Agave parryi and A. weberi tolerated salinity at higher levels than expected, and may show promise for cultivation in saline soils.

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Andrew Koeser, Sarah T. Lovell, Michael Evans, and J. Ryan Stewart

In recent years, biocontainers have been marketed as sustainable alternatives to petroleum-based containers in the green industry. However, biocontainers constructed with plant materials that are highly porous in nature (e.g., peat, wood fiber, straw) tend to require more frequent irrigation than conventional plastic products. As irrigation water sources become less abundant and more expensive, growers must consider water consumption in any assessment of their economic and environmental viability. This project evaluated plant growth and total water consumption for nine different biocontainers (seven organic alternatives, and two recently developed bioplastic alternatives) and a plastic control used to produce a short-term greenhouse crop, ‘Yellow Madness’ petunia (Petunia ×hybrida). Dry shoot weight and total water consumption differed by container type, with some of the more porous containers (wood fiber, manure, and straw) requiring more water and producing smaller plants by the end of the trial period. Intuitively, the more impervious plastic, bioplastic, and solid rice hull containers required the least irrigation to maintain soil moisture levels, though shoot dry weights varied among this group. Shoot dry weight was highest with the bioplastic sleeve and slotted rice hull containers. However, the latter of these two containers required a greater volume of water to stay above the drying threshold. Findings from this research suggest the new bioplastic sleeve may be a promising alternative to conventional plastic containers given the current production process.

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J. Ryan Stewart, Reid D. Landes, Andrew K. Koeser, and Andrea L. Pettay

Frequent episodes of water stress in managed landscapes have led the nursery industry to look for attractive woody species that perform well under extreme conditions of drought and flooding. We chose to evaluate three taxa with highly localized natural distributions in the United States, Calycanthus occidentalis (north–central California), Fraxinus anomala (northeastern Utah), and Pinckneya pubens (northeastern Florida), each of which may merit further use under cultivated conditions beyond their respective ranges. Although widespread cultivation of each taxon may not be possible as a result of limitations related to cold hardiness, we hypothesized that each species can tolerate extremes in soil moisture availability more so than their native habitats imply. Our objective was to characterize, under greenhouse conditions, how the quantity of soil water affects gas exchange of potted plants of each species. Plants were divided into five groups, each exposed to treatment conditions ranging from complete submersion to severe drought. Complete submersion killed plants of C. occidentalis and F. anomala, although in drought or severe drought conditions, C. occidentalis plants had lower net photosynthesis and less leaf area and plant dry weight than control plants. Net photosynthesis, leaf area, and plant dry weight of partially flooded plants, however, were not found to be significantly less than that of the control plants. Mean net photosynthetic levels and plant dry weights of severe drought, drought, and control F. anomala did not differ. While severe drought plants of P. pubens exhibited much lower levels of net photosynthesis, but not plant dry weights or leaf area, than the control plants, those exposed to drought, partial flood, and complete submersion were not found to differ in net photosynthesis levels from the control plants. Due to the sustained tolerance of F. anomala and P. pubens to a range of extreme soil moisture conditions, as exhibited by net photosynthetic responses, carbon accumulation, and survival, we conclude that use of these species in landscapes is warranted if invasiveness and other potential problems are not identified. Calycanthus occidentalis, however, appears unsuitable for cultivation in areas with organic soils greater than ≈66% and lower than ≈30% soil moisture content as a result of its high mortality in flooded conditions and poor physiological responses under dry conditions.

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Andrew K. Koeser, Sarah T. Lovell, Aaron C. Petri, Robin G. Brumfield, and J. Ryan Stewart

This study assessed the material and energy inputs required to produce a Petunia ×hybrida plant from initial propagation to delivery at a regional distribution center. Impacts were expressed in terms of their contribution to the carbon footprint or global warming potential (GWP) of a single finished plant in a ≈10-cm diameter container. Beyond this baseline assessment, the study investigated the secondary impacts (e.g., irrigation demand) associated with container type used. Life cycle assessment data were sourced from interviews, published literature, propriety data sources, direct metering at the greenhouse facility, and original findings from a series of university greenhouse experiments. Results show that a traditional plastic container accounts for ≈16% of overall CO2e emissions (0.544 kg) during petunia production. Although the container was a significant contributor to GWP, electrical consumption for supplemental lighting and irrigation during plug production proved to be the leading source of CO2e emissions (over 47%) in our model system. Differences in GWP when considering secondary impacts associated with the various biocontainers were minor, especially when compared with the other elements of production. Our results demonstrate that biocontainers could potentially be as or more sustainable than plastic pots once pot manufacturing and end-of-life data are considered. However, use of more efficient supplemental lighting sources may ultimately have the greatest impact on overall GWP for the production system assessed.

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Renee Conneway, Sven Verlinden, Andrew K. Koeser, Michael Evans, Rebecca Schnelle, Victoria Anderson, and J. Ryan Stewart

While research on the use of alternative containers for greenhouse production is growing, most studies have focused on a limited number of types of alternative containers and primarily on short-term greenhouse crops. With the recent release of several new bioplastic alternatives, comparisons to established alternative containers and production of longer rotation ornamental crops should be investigated. Our work, therefore, investigates the performance of ten commercially available alternative containers and their effects on both a short-term ‘Sunpatiens Compacta’ impatiens (Impatiens ×hybrida) and a long-term greenhouse crop ‘Elegans Ice’ lavender (Lavendula angustifolia) at four different locations. Results indicated that plant growth in terms of dry weight differed by container at most locations. Combined analysis of all locations showed that only straw and a bioplastic sleeve outperformed plastic pots in terms of shoot dry weight and then only after 12 weeks of production. Leachate pH, but not electrical conductivity (EC), varied by container in both the short- and long-term crop with alternative containers made from composted cow manure and peat showing consistently higher and lower pH readings, respectively. Postharvest container strength varied significantly by container, with the plastic control maintaining the highest puncture resistance after both 6 and 12 weeks, in some instances matched by the puncture strength of coconut fiber pots. Some alternative containers, in particular, wood, manure, and peat showed algal growth after 6 and 12 weeks of greenhouse production. We conclude that while some alternative containers were linked to increased growth, most showed growth equal to the plastic control, and could therefore make appropriate alternatives to plastic pots. However, changes in pH, low puncture strengths after production, higher denesting times, and algal growth on manure, wood, and peat may make these pots less desirable alternatives than other pots under investigation. However, other factors not studied here, such as compostability, biodegradability in the landscape, water use, consumer preference, aesthetics, compatibility with mechanized operations, and cost may also need to be taken into account when deciding on an appropriate container for greenhouse production.

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Brianna L. Ewing, Gregory M. Peck, Sihui Ma, Andrew P. Neilson, and Amanda C. Stewart

Hard cider production in the United States has increased dramatically during the past decade, but there is little information on how harvest and postharvest practices affect the chemistry of the resulting cider, including concentrations of organoleptically important flavanols. For 2 years we assessed fruit, juice, and cider from a total of five apple (Malus ×domestica Borkh.) cultivars in two experiments: sequential harvests and postharvest storage. Different cultivars were used in 2015 and 2016 with the exception of ‘Dabinett’, which was assessed in both years. There were no differences in polyphenol concentrations in cider made from fruit that was harvested on three separate occasions over a 4-week period in either 2015 or 2016. Fruit storage durations and temperatures had little influence on the chemistry when the experiment was conducted in 2015, but polyphenol concentration was greater after storage in the 2016 experiment. In 2016, total polyphenols in ‘Dabinett’ ciders were 51% greater after short-term storage at 10 °C and 67% greater after long-term storage at 1 °C than the control, which was not subjected to a storage treatment. In 2016, total polyphenols in ‘Binet Rouge’ ciders were 67% greater after short-term storage at 10 °C and 94% greater after long-term storage at 1 °C than the control. Although results varied among cultivars and harvest years, storing apples for longer periods of time and at warmer temperatures may be a strategy to increase polyphenol, particularly flavanol, concentrations in hard cider.

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Andrew K. Koeser, J. Ryan Stewart, Germán A. Bollero, Donald G. Bullock, and Daniel K. Struve

Transplanted trees are exposed to numerous stresses from the time of harvest until establishment in the landscape. Although an individual stress factor may be the sole cause of plant death or decline, it is more likely a combination of stress factors cause reduced growth or death after planting. In an effort to isolate the stresses associated with three critical stages in the transplanting process (i.e., initial harvest, handling, and transport), 5-cm-caliper, balled-and-burlapped Acer rubrum L. ‘Red Sunset’ (red maple) and Acer platanoides L. ‘Pond’ (Norway maple) trees at three sites (Urbana, IL; Union, IL; and Manitowoc, WI) were subjected to three treatments: root-pruned, handled, and transported. Effects of water stress, root severance, and root-ball disruption on twig elongation and tree survival were measured for each treatment and compared with unaltered control trees. Twig elongation was greater in unaltered control trees when compared with root-pruned trees. In addition, root-pruned trees exhibited greater twig elongation when compared with either handled or transported trees suggesting that although initial root severance did affect growth, it was not as detrimental as lifting and handling. In addition, twig elongation was not different between handled and transported trees. Water potential measurements ranged from –0.2 to –2.0 MPa, suggesting water stress was not a critical factor during the time of transplanting. Similarly, root-ball soil moisture varied little between treatments over the course of transplanting. Results suggest rough handling before and after transport should be minimized in an effort to maximize growth and transplant success.

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Michael R. Evans, Andrew K. Koeser, Guihong Bi, Susmitha Nambuthiri, Robert Geneve, Sarah Taylor Lovell, and J. Ryan Stewart

Nine commercially available biocontainers and a plastic control were evaluated at Fayetteville, AR, and Crystal Springs, MS, to determine the irrigation interval and total water required to grow a crop of ‘Cooler Grape’ vinca (Catharanthus roseus) with or without the use of plastic shuttle trays. Additionally, the rate at which water passed through the container wall of each container was assessed with or without the use of a shuttle tray. Slotted rice hull, coconut fiber, peat, wood fiber, dairy manure, and straw containers were constructed with water-permeable materials or had openings in the container sidewall. Such properties increased the rate of water loss compared with more impermeable bioplastic, solid rice hull, and plastic containers. This higher rate of water loss resulted in most of the biocontainers having a shorter irrigation interval and a higher water requirement than traditional plastic containers. Placing permeable biocontainers in plastic shuttle trays reduced water loss through the container walls. However, irrigation demand for these containers was still generally higher than that of the plastic control containers.

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Youping Sun, Genhua Niu, Andrew K. Koeser, Guihong Bi, Victoria Anderson, Krista Jacobsen, Renee Conneway, Sven Verlinden, Ryan Stewart, and Sarah T. Lovell

As the green industry is moving toward sustainability to meet the demands of society, the use of biocontainers as alternatives to petroleum-based plastic containers has drawn significant attention. Field trials of seven plantable biocontainers (coir, manure, peat, rice hull, soil wrap, straw, and wood fiber) were conducted in 2011 and 2012 at five locations in the United States to assess the influence of direct-plant biocontainers on plant growth and establishment and the rate of container decomposition in landscape. In 2011, container type did not affect the growth of any of the three species used in this study with an exception in one location. The three species were ‘Sunpatiens Compact Magenta’ new guinea impatiens (Impatiens ×hybrida), ‘Luscious Citrus’ lantana (Lantana camara), and ‘Senorita Rosalita’ cleome (Cleome ×hybrida). In 2012, the effect of container type on plant growth varied with location and species. Cleome, new guinea impatiens, and lantana plants grown in coir and straw containers were in general smaller than those in peat, plastic, rice hull, and wood fiber containers. After 3 to 4 months in the field, manure containers had on average the highest rate of decomposition at 88% for all five locations and two growing seasons. The levels of decomposition of other containers, straw, wood fiber, soil wrap, peat, coir, and rice hull were 47%, 46%, 42%, 38%, 25%, and 18%, respectively, in descending order. Plantable containers did not hinder plant establishment and posttransplant plant growth. The impact of container type on plant growth was smaller compared with that of location (climate). Similarly, the impact of plant species on pot decomposition was smaller compared with that of pot material.